Metal gate structure and method of forming the same

Abstract

The present invention provides a metal gate structure which is formed in a trench of a dielectric layer. The metal gate structure includes a work function metal layer and a metal layer. The work function metal layer is disposed in the trench and comprises a bottom portion and a side portion, wherein a ratio between a thickness of the bottom portion and a thickness of the side portion is between 2 and 5. The trench is filled with the metal layer. The present invention further provides a method of forming the metal gate structure.

What is claimed is: 
     
       1. A metal gate structure, which is disposed in a trench in a dielectric layer, comprising:
 a work function metal (WFM) layer disposed in the trench, wherein the WFM layer comprises a bottom portion and a side portion, and a ratio of a thickness of the bottom portion and a thickness of the side portion is between 2 and 5, the WFM layer comprises TiAl x Cu y , and x+y=3; and 
 a metal layer filled in the trench. 
 
     
     
       2. The metal gate structure according to  claim 1 , wherein the WFM layer further comprises a protruding portion disposed at an opening of the trench. 
     
     
       3. The metal gate structure according to  claim 2 , wherein a ratio of the thickness of the bottom portion and a thickness of the protruding portion is between 2 and 6. 
     
     
       4. The metal gate structure according to  claim 1 , wherein the WFM layer comprises titanium aluminides (TiAl), aluminum zirconium (ZrAl), aluminum tungsten (WAl), aluminum tantalum (TaAl) or aluminum hafnium (HfAl). 
     
     
       5. The metal gate structure according to  claim 1 , wherein the WFM layer comprises TiAl 3 . 
     
     
       6. The metal gate structure according to  claim 1 , wherein the WFM layer comprises Ni, Pd, Pt, Be, Ir, Te, Re, Ru, Rh, W, Mo, or WN, RuN, MoN, TiN, TaN, or WC, TaC, TiC, or TiAlN, TaAlN. 
     
     
       7. The metal gate structure according to  claim 1 , further comprising a metal oxide layer disposed between the WFM layer and the metal layer. 
     
     
       8. The metal gate structure according to  claim 7 , wherein the metal oxide layer comprises TiAlO. 
     
     
       9. The metal gate structure according to  claim 1 , wherein the metal layer comprises Al or Cu.